Quicksilver is a great productivity application for OS X, and a power user can really do quite a bit. Productivity blogger Merlin Mann has a nice write up of one of Quicksilver's more useful features—the "Append" feature.

To review, for you new kids, Quicksilver, when properly configured (more on that in a minute), will let you add a line of text to any text file on your Mac. As long as it s included in a QS catalog someplace, you re a few fast keystrokes away from capturing your brilliant but ephemeral idea without stopping what you re doing. This is huge, in practice, believe me.